In this paper Peter Klein's criticism of Wittgenstein in "Certainty: A Refutation of Scepticism" is addressed. Klein claims that, according to Wittgenstein, we attribute knowledge of a proposition p to a person only if that person is not certain of p. I argue that a careful reading of Wittgenstein's On Certainty reveals that there are two kinds of objective certainty that Wittgenstein had in mind; propositional objective certainty and normative objective certainty. Klein fails to distinguish between the two and uses what I call propositional objective certainty to make his point against Wittgenstein. I claim that when Wittgenstein said that knowledge and certainty belong to different categories he was talking of normative objective certainty and, therefore, that Klein's criticism is misplaced and attributes to Wittgenstein a position that is not his.